The present invention relates to a poppet valve seal mechanism, and more particularly, to a valve seal mechanism which prevents the seal member from being separated in a two port valve which seals a poppet valve using a seal member.
Conventionally, as the poppet valve seal mechanism of this kind, there is a know mechanism as shown in FIG. 8 in which a valve body 1 is formed with a dovetail groove 2, a width of an opening 2a of the groove 2 is smaller than that of the inside of the groove, a seal member 4 which has rubber resiliency and which is brought into contact with a valve seat 3 under pressure is mounted into the groove 2 so that the seal member 4 is prevented from falling out from the groove 2.
According to such a poppet valve seal mechanism, however, when a pressure-contacting force of the seal member 4 with respect to the valve seat 3 is great, or when a seal member 4 which is easily deformed is used, as shown in FIG. 9, there is a problem that the seal member 4 is completely embedded into the groove 2, the valve body 1 and the valve seat 3 are brought into direct contact with each other, a so-called metal touch is generated.
This metal touch may cause metal powder by friction and wear and thus, the metal touch must be avoided as less as possible in equipment which requires clean environment such as a semiconductor producing apparatus.
It is a technical object of the present invention is to provide a poppet valve seal mechanism in which a seal member does not fall out from a groove, and the metal touch is not generated.
To achieve the above object, the present invention provides a poppet valve seal mechanism in which a valve seat is provided in a flow path, a valve body is allowed to move in a direction perpendicular to a valve seat surface of the valve body, thereby bringing the valve body into contact and away from the valve seat to open and close the flow path, wherein an annular seal member made of resilient body for sealing between the valve body and the valve seat is mounted to an annular groove provided in one of the valve seat and the valve body, the groove is formed such that a width of its opening is smaller than a maximum width of inside of the groove, and an area of cross section is smaller than that of the seal member, a maximum width of a portion of the seal member accommodated in the groove is formed larger than a width of the opening of the groove, the seal member projects from the opening of the groove in any of state in which the seal member is brought into contact with an opposed seal surface under pressure and a state in which the seal member is not brought into contact with the opposed seal surface under pressure.
With the above structure, it is possible to avoid a so-called metal touch in which the valve body 1 and the valve seat 3 in FIG. 9 are brought into direct contact with each other when the seal member is brought into contact with the opposed seal surface under pressure, and it is possible to prevent metal powder from being generated by friction and wear caused by the metal touch.
According to the invention, in the above poppet valve seal mechanism, the opening of the groove has a constant width over its entire periphery, the inside of the groove is formed of an inner wall and a pair of side wall surfaces which are connected from opposite ends of the bottom wall surface to the opening, the seal member has a cross section shape which forms a gap between inner walls extending from the bottom wall surface of the groove to the side wall surfaces, the side wall surfaces of the inner wall forming the gap is formed with a communication hole which bring the inside of the groove and an outside of the groove into communication with each other.
With the above structure, when the seal member is brought into contact with the opposed seal surface under pressure, the metal touch can be avoided and air in the gap formed between the seal member and the inner wall of the groove is allowed to guide outside the groove through the communication hole, and it is possible to bring the surface of the seal member and the inner wall of the groove into substantially close contact with each other. Therefore, with the synergism caused by narrowing the opening of the groove, it is possible to more reliably prevent the seal member from falling out from the groove when the seal member is separated from the opposed seal surface.
When the gap is formed between the seal member and the inner wall on an inner periphery of the groove and between the seal member and the inner wall of the outer periphery of the groove, it is preferable that the communication hole is formed in each of the side wall surface of the inner periphery and the side wall surface of the outer periphery.
The inside of the groove can be brought into communication with passages located on the opposite side of the valve body with each other by means of the communication holes.
In the above poppet valve seal mechanism, the valve body can be provided in the flow path which connects the two ports to each other, and one of the two ports can be connected to the vacuum pump.
A cross section of the seal member can be circular in shape.
It is more preferable that the following relations are established: B/A=0.80 to 0.95, B/D=0.70 to 0.85, E/A=0.25 to 0.35, wherein A is a diameter of the seal member, E is a length of a projecting portion of the seal member projecting from the groove, B is a width of the opening of the groove, and D is a width of the inside of the groove.
The poppet valve seal mechanism of the present invention can exhibit excellent sealing ability even if the seal member is made of any material, but the poppet valve seal mechanism is especially effective when the seal mechanism employs an O-ring or the like made of such resilient body that deformation caused by an external force is less prone to be restored, i.e., plastic deformation is easily maintained and the material is easily attached.
FIG. 1 is a vertical sectional view of an essential portion of a poppet valve having a seal mechanism according to a first embodiment of the present invention.
FIG. 2 is an enlarged sectional view of a poppet valve seal mechanism under no load according to the first embodiment of the invention.
FIG. 3 is an enlarged sectional view of the poppet valve seal mechanism under no load according to the first embodiment of the invention.
FIG. 4 is a vertical sectional view of an essential portion of a poppet valve having a seal mechanism according to a second embodiment of the invention.
FIG. 5 is an enlarged sectional view of a poppet valve seal mechanism according to the second embodiment of the invention, taken along a Ixe2x80x94I line in FIG. 7.
FIG. 6 is an enlarged sectional view of a seal member used in the poppet valve seal mechanism of the second embodiment of the invention.
FIG. 7 is an enlarged view of the valve body of the second embodiment of the invention as viewed from its bottom.
FIG. 8 is an enlarged sectional view of a conventional poppet valve seal mechanism under no load.
FIG. 9 is an enlarged sectional view of the conventional poppet valve seal mechanism under no load.
FIG. 10 is an enlarged sectional view of a groove in a poppet valve seal mechanism previously developed by the present inventor, taken along a line IIxe2x80x94II in FIG. 11.
FIG. 11 is an enlarged view of a valve body of a poppet valve seal mechanism previously developed by the present inventor as viewed from its bottom.